Olefin metathesis is a catalytic process including, as a key step, a reaction between a first olefin and a first transition metal alkylidene complex, thus producing an unstable intermediate metallacyclobutane ring which then undergoes transformation into a second olefin and a second transition metal alkylidene complex according to equation (1) hereunder. Reactions of this kind are reversible and in competition with one another, so the overall result heavily depends on their respective rates and, when formation of volatile or insoluble products occur, displacement of equilibrium.

Several exemplary but non-limiting types of metathesis reactions for mono-olefins or di-olefins are shown in equations (2) to (5) herein-after. Removal of a product, such as ethylene in equation (2), from the system can dramatically alter the course and/or rate of a desired metathesis reaction, since ethylene reacts with an alkylidene complex in order to form a methylene (M=CH2) complex, which is the most reactive and also the least stable of the alkylidene complexes.

Of potentially greater interest than homo-coupling (equation 2) is cross-coupling between two different terminal olefins. Coupling reactions involving dienes lead to linear and cyclic dimers, oligomers, and, ultimately, linear or cyclic polymers (equation 3). In general, the latter reaction called acyclic diene metathesis (hereinafter referred to as ADMET) is favoured in highly concentrated solutions or in bulk, while cyclisation is favoured at low concentrations. When intra-molecular coupling of a diene occurs so as to produce a cyclic alkene, the process is called ring-closing metathesis (hereinafter referred to as RCM) (equation 4). Strained cyclic olefins can be opened and oligomerised or polymerised (ring opening metathesis polymerisation (hereinafter referred to as ROMP) shown in equation 5). When the alkylidene catalyst reacts more rapidly with the cyclic olefin (e.g. a norbornene or a cyclobutene) than with a carbon-carbon double bond in the growing polymer chain, then a “living ring opening metathesis polymerisation” may result, i.e. there is little termination during or after the polymerization reaction.
A large number of catalyst systems comprising well-defined single component metal carbene complexes have been prepared and utilized in olefin metathesis. One major development in olefin metathesis was the discovery of the ruthenium and osmium carbene complexes by Grubbs and co-workers. U.S. Pat. No. 5,977,393 discloses Schiff base derivatives of such compounds, which are useful as olefin metathesis catalysts, wherein the metal is coordinated by a neutral electron donor, such as a triarylphosphine or a tri(cyclo)alkylphosphine, and by an anionic ligand. Such catalysts show an improved thermal stability while maintaining metathesis activity even in polar protic solvents. They are also able to promote cyclisation of, for instance, diallylamine hydrochloride into dihydropyrrole hydrochloride. Remaining problems to be solved with the carbene complexes of Grubbs are (i) improving both catalyst stability (i.e. slowing down decomposition) and metathesis activity at the same time and (ii) broadening the range of organic products achievable by using such catalysts, e.g. providing ability to ring-close highly substituted dienes into tri- and tetra-substituted olefins.
International patent application published as WO 99/00396 discloses at least penta-coordinated ruthenium and osmium complexes including two anionic ligands and two monodentate neutral electron donor ligands and further wherein one of the coordinating ligands is a heteroatom-containing alkylidene of the formula ═CH—Z—R, wherein Z is sulfur, hydrocarbylphosphino, oxygen or hydrocarbylamino, and wherein R is hydrocarbyl.
International patent application published as WO 03/062253 discloses five-coordinate metal complexes, salt, solvates or enantiomers thereof, comprising a carbene ligand, a multidentate ligand and one or more other ligands, wherein at least one of said other ligands is a constraint steric hindrance ligand having a pKa of at least 15. More specifically, the said document discloses five-coordinate metal complexes having one of the general formulae (IA) and (IB) referred to in FIG. 1, wherein:                M is a metal selected from the group consisting of groups 4, 5, 6, 7, 8, 9, 10, 11 and 12 of the Periodic Table, preferably a metal selected from ruthenium, osmium, iron, molybdenum, tungsten, titanium, rhenium, copper, chromium, manganese, rhodium, vanadium, zinc, gold, silver, nickel and cobalt;        Z is selected from the group consisting of oxygen, sulphur, selenium, NR″″, PR″″, AsR″″ and SbR″″;        R″, R′″ and R″″ are each a radical independently selected from the group consisting of hydrogen, C1-6 alkyl, C3-8 cycloalkyl, C1-6 alkyl-C1-6 alkoxysilyl, C1-6 alkyl-aryloxysilyl, C1-6 alkyl-C3-10 cycloalkoxysilyl, aryl and heteroaryl, or R″ and R′″ together form an aryl or heteroaryl radical, each said radical (when different from hydrogen) being optionally substituted with one or more, preferably 1 to 3, substituents R5 each independently selected from the group consisting of halogen atoms, C1-6 alkyl, C1-6 alkoxy, aryl, alkylsulfonate, aryisulfonate, alkylphosphonate, arylphosphonate, C1-6 alkyl-C1-6 alkoxysilyl, C1-6 alkyl-aryloxysilyl, C1-6 alkyl-C3-10 cycloalkoxysilyl, alkylammonium and arylammonium;        R′ is either as defined for R″, R′″ and R″″ when included in a compound having the general formula (IA) or, when included in a compound having the general formula (IB), is selected from the group consisting of C1-6 alkylene and C3-8 cycloalkylene, the said alkylene or cycloalkylene group being optionally substituted with one or more substituents R5;        R1 is a constraint steric hindrance group having a pKa of at least about 15;        R2 is an anionic ligand;        R3 and R4 are each hydrogen or a radical selected from the group consisting of C1-20 alkyl, C2-20 alkenyl, C2-20 alkynyl, C1-20 carboxylate, C1-20 alkoxy, C2-20 alkenyloxy, C2-20 alkynyloxy, aryl, aryloxy, C1-20 alkoxycarbonyl, C1-8 alkylthio, C1-20 alkylsulfonyl, C1-20 alkylsulfinyl C1-20 alkylsulfonate, arylsulfonate, C1-20 alkylphosphonate, arylphosphonate, C1-20 alkylammonium and arylammonium;        R′ and one of R3 and R4 may be bonded to each other to form a bidentate ligand;        
R′″ and R″″ may be bonded to each other to form an aliphatic ring system including a heteroatom selected from the group consisting of nitrogen, phosphorous, arsenic and antimony;                R3 and R4 together may form a fused aromatic ring system, and        y represents the number of sp2 carbon atoms between M and the carbon atom bearing R3 and R4 and is an integer from 0 to 3 inclusive,        salts, solvates and enantiomers thereof.        
These five-coordinate metal complexes of WO 03/062253 proved to be very efficient olefin metathesis catalysts. International patent application published as WO 2005/035121 discloses at least tetra-coordinated metal complexes, salts, solvates and enantiomers thereof, comprising:                a multidentate ligand being coordinated with the metal by means of a nitrogen atom and at least one heteroatom selected from the group consisting of oxygen, sulphur, selenium, nitrogen, phosphorus, arsenic and antimony, wherein each of nitrogen, phosphorus, arsenic and antimony is substituted with a radical R″″ selected from the group consisting of hydrogen, C1-7 alkyl, C3-10 cycloalkyl, aryl and heteroaryl;        a non-anionic unsaturated ligand L1 selected from the group consisting of aromatic and unsaturated cycloaliphatic groups, preferably aryl, heteroaryl and C4-20 cycloalkenyl groups, the said aromatic or unsaturated cycloaliphatic group being optionally substituted with one or more C1-7 alkyl groups or electron-withdrawing groups such as, but not limited to, halogen, nitro, cyano, (thio)carboxylic acid, (thio)carboxylic acid (thio)ester, (thio)carboxylic acid (thio)amide, (thio)carboxylic acid anhydride and (thio) carboxylic acid halide; and        a non-anionic ligand L2 selected from the group consisting of C1-7 alkyl, C3-10 cycloalkyl, aryl, arylalkyl, alkylaryl and heterocyclic, the said group being optionally substituted with one or more preferably electron-withdrawing substituents such as, but not limited to, halogen, nitro, cyano, (thio)carboxylic acid, (thio)carboxylic acid (thio)ester, (thio)carboxylic acid (thio)amide, (thio)carboxylic acid anhydride and (thio) carboxylic acid halide.        
The multidentate ligand of such an at least tetra-coordinated metal complex may be a bidentate or tridentate Schiff base. WO 2005/035121 also discloses hexa-coordinated metal complexes, salts, solvates and enantiomers thereof, comprising:                a multidentate ligand being coordinated with the metal by means of a nitrogen atom and at least one heteroatom selected from the group consisting of oxygen, sulphur, selenium, nitrogen, phosphorus, arsenic and antimony, wherein each of nitrogen, phosphorus, arsenic and antimony is substituted with a radical R″″ selected from the group consisting of hydrogen, C1-7 alkyl, C3-10 cycloalkyl, aryl and heteroaryl;        at least one non-anionic bidentate ligand L3 being different from the multidentate ligand; and        at most two anionic ligands L4, wherein one or more of said anionic ligands L4 may be each replaced with a solvent S, in which case the said hexa-coordinated metal complex is a cationic species associated with an anion A.The multidentate ligand of such an at least hexa-coordinated metal complex may be a bidentate or tridentate Schiff base. These tetra-coordinated and hexa-coordinated metal complexes of WO 2005/035121 proved to be very efficient olefin metathesis catalysts, especially in the ring opening metathesis polymerisation of norbornene and derivatives thereof.        
However there is a continuous need in the art for improving catalyst efficiency, i.e. improving the yield of the reaction catalysed by the said catalyst component after a certain period of time under given conditions (e.g. temperature, pressure, solvent and reactant/catalyst ratio) or else, at a given reaction yield, providing milder conditions (lower temperature, pressure closer to atmospheric pressure, easier separation and purification of product from the reaction mixture) or requiring a smaller amount of catalyst (i.e. a higher reactant/catalyst ratio) and thus resulting in more economic and environment-friendly operating conditions. This need is still more stringent for use in reaction-injection molding (RIM) processes such as, but not limited to, the bulk polymerisation of endo- or exo-dicyclopentadiene, or formulations thereof.
WO 93/20111 describes osmium- and ruthenium-carbene compounds with phosphine ligands as purely thermal catalysts for ring-opening metathesis polymerization of strained cycloolefins, in which cyclodienes such as dicyclopentadiene act as catalyst inhibitors and cannot be polymerized. This is confirmed for instance by example 3 of U.S. Pat. No. 6,284,852, wherein dicyclopentadiene did not yield any polymer, even after days in the presence of certain ruthenium carbene complexes having phosphine ligands. However, U.S. Pat. No. 6,235,856 teaches that dicyclopentadiene is accessible to thermal metathesis polymerization with a single-component catalyst if carbene-free ruthenium(II)- or osmium(II)-phosphine catalysts are used.
U.S. Pat. No. 6,284,852 discloses enhancing the catalytic activity of a ruthenium carbene complex of the formula AxLyXzRu═CHR′, wherein x=0, 1 or 2, y=0, 1 or 2, and z=1 or 2 and wherein R′ is hydrogen or a substituted or unsubstituted alkyl or aryl, L is any neutral electron donor, X is any anionic ligand, and A is a ligand having a covalent structure connecting a neutral electron donor and an anionic ligand, by the deliberate addition of specific amounts of acid not present as a substrate or solvent, the said enhancement being for a variety of olefin metathesis reactions including ROMP, RCM, ADMET and cross-metathesis and dimerization reactions. According to U.S. Pat. No. 6,284,852, organic or inorganic acids may be added to the catalysts either before or during the reaction with an olefin, with longer catalyst life being observed when the catalyst is introduced to an acidic solution of olefin monomer. The amounts of acid disclosed in examples 3 to 7 of U.S. Pat. No. 6,284,852 range from 0.3 to 1 equivalent of acid, with respect to the alkylidene moiety. In particular, the catalyst systems of example 3 (in particular catalysts being Schiff-base-substituted complexes including an alkylidene ligand and a phosphine ligand) in the presence of HCl as an acid achieve ROMP of dicyclopentadiene within less than 1 minute at room temperature in the absence of a solvent, and ROMP of an oxanorbornene monomer within 15 minutes at room temperature in the presence of a protic solvent (methanol), however at monomer/catalyst ratios which are not specified.
U.S. Pat. No. 6,284,852 also shows alkylidene ruthenium complexes which, after activation in water with a strong acid, quickly and quantitatively initiate living polymerization of water-soluble polymers, resulting in a significant improvement over existing ROMP catalysts. It further alleges that the propagating species in these reactions is stable (a propagating alkylidene species was observed by proton nuclear magnetic resonance) and that the effect of the acid in the system appears to be twofold: in addition to eliminating hydroxide ions which would cause catalyst decomposition, catalyst activity is also enhanced by protonation of phosphine ligands. It is also taught that, remarkably, the acids do not react with the ruthenium alkylidene bond.
Although providing an improvement over existing ROMP catalysts, the teaching of U.S. Pat. No. 6,284,852 is however limited in many aspects, namely:                because its alleged mechanism of acid activation involves the protonation of phosphine ligands, it is limited to alkylidene ruthenium complexes including at least one phosphine ligand;        it does not disclose reacting a Schiff-base-substituted ruthenium complex with an acid under conditions such that said acid at least partly cleaves a bond between ruthenium and the Schiff base ligand of said complex.        
U.S. Pat. No. 6,284,852 does not either teach the behaviour, in the presence of an acid, of ruthenium complexes wherein ruthenium is coordinated with a vinylidene ligand, an allenylidene ligand or a N-heterocyclic carbene ligand.
U.S. Pat. No. 6,284,852 therefore has left open ways for the study of multi-coordinated metal complexes, in particular multicoordinated ruthenium and osmium complexes in an acidic, preferably a strongly acidic, environment when used for olefin or alkyne metathesis reactions including ROMP, RCM, ADMET, and for cross-metathesis and dimerization reactions.
Therefore one goal of this invention is the design of new and useful catalytic species, especially based on multicoordinated transition metal complexes, having unexpected properties and improved efficiency in olefin or alkyne metathesis reactions.
Another goal of this invention is to efficiently perform olefin or alkyne metathesis reactions, in particular ring opening polymerization of strained cyclic olefins (including cationic forms of such monomers such as, but not limited to, strained cyclic olefins including quaternary ammonium salts), in the presence of multicoordinated transition metal complexes without being limited by the requirement of a phosphine ligand in said complexes.
There is also a specific need in the art, which is yet another goal of this invention, for improving reaction-injection molding (RIM) processes, resin transfer molding (RTM) processes, pultrusion, filament winding and reactive rotational molding (RRM) processes such as, but not limited to, the bulk polymerisation of endo- or exo-dicyclopentadiene, or copolymerization thereof with other monomers, or formulations thereof. More specifically there is a need to improve such processes which are performed in the presence of multicoordinated transition metal complexes, in particular ruthenium complexes, having various combinations of ligands but which do not necessarily comprise phosphine ligands. All the above needs constitute the various goals to be achieved by the present invention, nevertheless other advantages of this invention will readily appear from the following description.